In utero delivery of rAAV2/9 induces neuronal expression of the transgene in the brain: towards new models of Parkinson's disease.

Animal models are essential tools for basic pathophysiological research as well as validation of therapeutic strategies for curing human diseases. However, technical difficulties associated with classical transgenesis approaches in rodent species higher than Mus musculus have prevented this long-awaited development. The availability of viral-mediated gene delivery systems in the past few years has stimulated the production of viruses with unique characteristics. For example, the recombinant adeno-associated virus serotype 9 (rAAV2/9) crosses the blood-brain barrier, is capable of transducing developing cells and neurons after intravenous injection and mediates long-term transduction. Whilst post-natal delivery is technically straightforward, in utero delivery bears the potential of achieving gene transduction in neurons at embryonic stages during which the target area is undergoing development. To test this possibility, we injected rAAV2/9 carrying either A53T mutant human α-synuclein or green fluorescent protein, intracerebroventricularly in rats at embryonic day 16.5. We observed neuronal transgene expression in most regions of the brain at 1 and 3 months after birth. This proof-of-concept experiment introduces a new opportunity to model brain diseases in rats.

Identification of distinct pathological signatures induced by patient-derived α-synuclein structures in nonhuman primates.

Dopaminergic neuronal cell death, associated with intracellular α-synuclein (α-syn)-rich protein aggregates [termed "Lewy bodies" (LBs)], is a well-established characteristic of Parkinson's disease (PD). Much evidence, accumulated from multiple experimental models, has suggested that α-syn plays a role in PD pathogenesis, not only as a trigger of pathology but also as a mediator of disease progression through pathological spreading. Here, we have used a machine learning-based approach to identify unique signatures of neurodegeneration in monkeys induced by distinct α-syn pathogenic structures derived from patients with PD. Unexpectedly, our results show that, in nonhuman primates, a small amount of singular α-syn aggregates is as toxic as larger amyloid fibrils present in the LBs, thus reinforcing the need for preclinical research in this species. Furthermore, our results provide evidence supporting the true multifactorial nature of PD, as multiple causes can induce a similar outcome regarding dopaminergic neurodegeneration.